Direct digital synthesis is a method of producing an analog waveform-usually a sine wave—by generating a time-varying signal in digital form and then performing a digital-to-analog conversion. Because operations within a DDS device may be primarily digital, such a device may offer fast switching between output frequencies, fine frequency resolution, and operation over a broad spectrum of frequencies. With advances in design and process technology, today's DDS devices may be very compact and may draw little power.
In some cases, a DDS may be used to digitally generate signals for transmission to a circuit-under-test. These synthesizers may be configured to receive digital data words from a source device and to convert these digital signals to analog signals for transmission to the circuit-under-test.
In order to generate a sinusoidal wave a number of different methods may be used. In the past, the generation of sine waves has previously been implemented by calculating a finite length array, loading the array into a memory, cycling through the array, and applying successive values of that array to a digital-to-analog converter (DAC) input. However, the finite number of points that may be required by this technique may limit the frequencies that may be synthesized in much the same way that a discrete Fourier transform differs from a continuous Fourier transform. Moreover, in the past, the implementation of a wave generation algorithm often required the use of trigonometric look-up tables.